Trifluoroacetic acid

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Trifluoroacetic acid
IUPAC name

2,2,2-Trifluoroethanoic acid

Other names

Perfluoroacetic acid
Trifluoroethanoic acid
TFA

Identifiers
CAS number 76-05-1 YesY
PubChem 6422
ChemSpider 10239201 YesY
UNII E5R8Z4G708 YesY
ChEBI CHEBI:45892 N
ChEMBL CHEMBL506259 YesY
RTECS number AJ9625000
Jmol-3D images Image 1
Properties
Molecular formula C2HF3O2
Molar mass 114.02 g/mol
Appearance colorless liquid
Density 1.489 g/cm3, 20 °C
Melting point −15.4 °C; 4.3 °F; 257.8 K
Boiling point 72.4 °C; 162.3 °F; 345.5 K
Solubility in water miscible
Acidity (pKa) 0.23 [1]
Hazards
MSDS External MSDS
R-phrases R20 R35 R52/53
S-phrases S9 S26 S27 S28 S45 S61
Main hazards Highly corrosive
NFPA 704
1
3
1
Flash point −3 °C; 27 °F; 270 K
Related compounds
Related perfluorinated acids Perfluorooctanoic acid
Perfluorononanoic acid
Related compounds Acetic acid
Trichloroacetic acid
 N (verify) (what is: YesY/N?)
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
Infobox references

Trifluoroacetic acid (TFA) is the organofluorine compound with the formula CF3CO2H. It is a colourless liquid with a sharp odor. It is a ~34,000-fold stronger acid than acetic acid due to the influence of the electronegative trifluoromethyl group. TFA is widely used in organic chemistry.

Synthesis

TFA is prepared industrially by the electrofluorination of acetyl chloride and acetic anhydride, followed by hydrolysis of the resulting trifluoroacetyl fluoride:[2]

CH
3COCl + 4 HF → CF
3COF + 3 H
2 + HCl
CF
3COF + H
2O → CF
3COOH + HF

Where desired, this compound may be dried by addition of trifluoroacetic anhydride.[3]

An older route to TFA proceeds via the oxidation of 1,1,1-trifluoro-2,3,3-trichloropropene with potassium permanganate. The trifluorotrichloropropene can be prepared by Swarts fluorination of hexachloropropene.

TFA occurs naturally in sea water, but only in small concentrations (<200 ng/L).[4][5]

Uses

TFA is the precursor to many other fluorinated compounds such as trifluoroacetic anhydride and 2,2,2-trifluoroethanol.[2] It is a reagent used in organic synthesis because of a combination of convenient properties: volatility, solubility in organic solvents, and its strength as an acid.[6] TFA is also less oxidizing than sulfuric acid but more readily available in anhydrous form than many other acids. One complication to its use is that TFA forms an azeotrope with water (b. p. 105 °C).

TFA is popularly used as a strong acid in peptide synthesis and other organic synthesis to remove the t-butoxycarbonyl protecting group.[7][8]

At a low concentration, TFA is used as an ion pairing agent in liquid chromatography (HPLC) of organic compounds, particularly peptides and small proteins. TFA is a versatile solvent for NMR spectroscopy (for materials stable in acid). It is also used as a calibrant in mass spectrometry.[9]

TFA is used to produce trifluoroacetate salts.[10]

See also

References

  1. ↑ Ref 1 in Milne, J. B.; Parker, T. J. (1981). "Dissociation constant of aqueous trifluoroacetic acid by cryoscopy and conductivity". Journal of Solution Chemistry 10 (7): 479. doi:10.1007/BF00652082. 
  2. ↑ 2.0 2.1 G. Siegemund, W. Schwertfeger, A. Feiring, B. Smart, F. Behr, H. Vogel, B. McKusick (2005), "Fluorine Compounds, Organic", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a11_349 
  3. ↑ Wilfred L.F. Armarego and Christina Li Lin Chai. "Chapter 4 - Purification of Organic Chemicals". Purification of Laboratory Chemicals (6th Ed. ed.). doi:10.1016/B978-1-85617-567-8.50012-3. 
  4. ↑ "Trifluoroacetate in ocean waters". Environ. Sci. Technol. 36 (1): 12–5. January 2002. Bibcode:2002EnST...36...12P. doi:10.1021/es0221659. PMID 11811478. 
  5. ↑ "Trifluoroacetate profiles in the Arctic, Atlantic, and Pacific Oceans". Environ. Sci. Technol. 39 (17): 6555–60. September 2005. Bibcode:2005EnST...39.6555S. doi:10.1021/es047975u. PMID 16190212. 
  6. ↑ Eidman, K. F.; Nichols, P. J. (2004). "Trifluoroacetic Acid". In L. Paquette. Encyclopedia of Reagents for Organic Synthesis. New York: J. Wiley & Sons. doi:10.1002/047084289. 
  7. ↑ Lundt, Behrend F.; Johansen, Nils L.; Vølund, Aage; Markussen, Jan (1978). "Removal of t-Butyl and t-Butoxycarbonyl Protecting Groups with Trifluoroacetic acid". International Journal of Peptide and Protein Research 12 (5): 258–268. doi:10.1111/j.1399-3011.1978.tb02896.x. PMID 744685. 
  8. ↑ Andrew B. Hughes. "1. Protection Reactions". In Vommina V. Sureshbabu, Narasimhamurthy Narendra. Amino Acids, Peptides and Proteins in Organic Chemistry: Protection Reactions, Medicinal Chemistry, Combinatorial Synthesis 4. doi:10.1002/9783527631827.ch1. 
  9. ↑ Stout, Steven J.; Dacunha, Adrian R. (1989). "Tuning and calibration in thermospray liquid chromatography/mass spectrometry using trifluoroacetic acid cluster ions". Analytical Chemistry 61 (18): 2126. doi:10.1021/ac00193a027. 
  10. ↑ O. Castano, A. Cavallaro, A. Palau, J. C. Gonzalez, M. Rossell, T. Puig, F. Sandiumenge, N. Mestres, S. Pinol, A. Pomar, and X. Obradors (2003). "High quality YBa2Cu3O7 thin films grown by trifluoroacetates metal-organic deposition". Superconductor Science and Technology 16 (1): 45–53. Bibcode:2003SuScT..16...45C. doi:10.1088/0953-2048/16/1/309. 
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